Thanks for the reply man, sorry for the late post! It had never done that before and the only thing I had changed was the power setting. I set it to auto-shutdown after 2 hours of inactivity. I have since turned off the auto-shutdown feature and it hasn't done that at all! So weird, I guess the receiver considers itself inactive if you're just sitting there watching stuff for a while? If you don't press any buttons or anything like that? Not sure what that's about but it seems to be just fine again.
Again, thanks for the reply! I'll keep an eye on it and if it does it again I'll call Yamaha!